Methods and appartus for crossing occlusions in blood vessels

ABSTRACT

This disclosure is directed to a device for facilitating treatment via a vascular wall defining a vascular lumen containing an occlusion therein. The device includes an intravascular device including a shaft having a distal end and a proximal end. The device includes a handle assembly fixed about the proximal end of the shaft, the handle assembly including a first portion. Rotation of the first portion in a first direction about a longitudinal axis of the shaft causes rotation of the shaft in the first direction when a torque applied by the first portion to the shaft is below a first maximum torque. Further rotation of the first portion in the first direction about a longitudinal axis of the shaft does not cause rotation of the shaft in the first direction when the torque applied by the first portion to the shaft is equal to or above the first maximum torque.

CROSS-REFERENCES TO RELATED APPLICATIONS

The present application is a continuation application of U.S. patentapplication Ser. No. 13/946,265, filed Jul. 19, 2013, which is acontinuation of U.S. patent application Ser. No. 13/443,860, filed Apr.10, 2012, now U.S. Pat. No. 8,496,679, which is a continuationapplication of U.S. patent application Ser. No. 12/453,009, filed Apr.27, 2009, now U.S. Pat. No. 8,172,863 which claims priority to U.S.Provisional Application No. 61/048,398, filed Apr. 28, 2008 under 37C.F.R. §1.78, the complete disclosures of which are incorporated hereinby reference.

FIELD OF THE INVENTION

Embodiments of the inventions, described herein relate to devices andassociated methods for the treatment of chronic total occlusions. Moreparticularly, embodiments of the inventions described herein relate todevices and methods for crossing chronic total occlusions andestablishing a pathway blood flow past the chronic total occlusions.

BACKGROUND OF THE INVENTION

Due to age, high cholesterol and other contributing factors, a largepercentage of the population has arterial atherosclerosis that totallyoccludes portions of the patient's vasculature and presents significantrisks to patient health. For example, in the case of a total occlusionof a coronary artery, the result may be painful angina, loss of cardiactissue or patient death. In another example, complete occlusion of thefemoral and/or popliteal arteries in the leg may result in limbthreatening ischemia and limb amputation.

Commonly known endovascular devices and techniques are eitherinefficient (time consuming procedure), have a high risk of perforatinga vessel (poor safety) or fail to cross the occlusion (poor efficacy).Physicians currently have difficulty visualizing the native vessellumen, can not accurately direct endovascular devices toward thevisualized lumen, or fail to advance devices through the lesion. Bypasssurgery is often the preferred treatment for patients with chronic totalocclusions, but less invasive techniques would be preferred.

Described herein are devices and methods employed to exploit thevascular wall of a vascular lumen for the purpose of bypassing a totalocclusion of an artery. Exploitation of a vascular wall may involve thepassage of an endovascular device into and out of said wall which iscommonly and interchangeably described as false lumen access, intramuralaccess, submedial access or in the case of this disclosure, subintimalaccess.

SUMMARY OF THE INVENTION

In one aspect, the present disclosure is directed to a device forfacilitating treatment of a blood vessel. The device includes a shafthaving a distal end and a proximal end. The device further includes ahandle assembly fixed about the proximal end of the shaft, the handleassembly including a first portion. Further rotation of the firstportion in a first direction about a longitudinal axis of the shaftcauses rotation of the shaft in the first direction when a torqueapplied by the first portion to the shaft is below a first maximumtorque. Still further, rotation of the first portion in the firstdirection about the longitudinal axis of the shaft does not causerotation of the shaft in the first direction when the torque applied bythe first portion to the shaft is above the first maximum torque.

In another aspect, the present disclosure is directed to a method offacilitating treatment of a blood vessel. The method may includeproviding a medical device shaft having a distal end and a proximal endand providing a handle assembly fixed to the proximal end of the shaft.The handle assembly may include a first portion. Further rotation of thefirst portion in a first direction about a longitudinal axis of theshaft causes rotation of the shaft in the first direction when a torqueapplied by the first portion to the shaft is below a first maximumtorque. Still further rotation of the first portion in the firstdirection about the longitudinal axis of the shaft does not causerotation of the shaft in the first direction when the torque applied bythe first portion to the shaft is above the first maximum torque. Themethod may further include rotating the first portion of the handleassembly in a first direction about the longitudinal axis, wherein therotating applies a torque to the shaft below the first maximum torque,and wherein the rotating causes the shaft to rotate.

Additional objects and advantages of the invention will be set forth inpart in the description which follows, and in part will be obvious fromthe description, or may be learned by practice of the invention. Theobjects and advantages of the invention will be realized and attained bymeans of the elements and combinations particularly pointed out in theappended claims.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive of the invention, as claimed.

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrates embodiments of the invention andtogether with the description, serve to explain the principles of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of a human heart. The heartincludes a plurality of coronary arteries that are all susceptible toocclusion. Occlusions can significantly reduce blood flow to distalportions of the coronary arteries. Under certain physiologicalcircumstances and given sufficient time, some occlusions may becometotal or complete occlusions.

FIG. 2 is an enlarged view further illustrating a portion of the heartshown in the previous figure. In FIG. 2, a total occlusion is shownblocking one of the coronary arteries of the heart. The presence of theocclusion in the coronary artery may result in inadequate oxygenation ofcardiac muscle located distal of the occlusion.

FIG. 3 is a cross-sectional view of an artery having a wall. The wall ofthe artery is shown having three layers. The outermost layer of wall isthe adventitia and the innermost layer of wall is the intima. Thetissues extending between intima and adventitia may be collectivelyreferred to as the media. In FIG. 4, an occlusion is blocking the truelumen of the artery. The distal tip of a crossing device has beenpositioned in the true lumen of the artery near the occlusion. Methodsdescribed in this document may include the step of advancing the distalend of the crossing device to a location distal of the occlusion in thecoronary artery. These methods may also include the step of advancingthe crossing device between the occlusion and the adventitia of theartery.

FIG. 4 is a plan view showing an assembly including the crossing deviceshown in the previous figure. In the embodiment of FIG. 4, a handleassembly is coupled to the crossing device. A physician may use thehandle assembly to rotate the crossing device. Rotation of crossingdevice can be achieved, for example, by rolling the handle assemblybetween the thumb and foreigner of two hands as shown in FIG. 4.

FIG. 5 is an enlarged plan view showing the handle assembly shown in theprevious figure. The handle assembly comprises a handle housing disposedabout a handle axle. In the embodiment of FIG. 5, the handle axle isfixed to a shaft of the crossing device.

FIG. 6 is a partial cross-sectional view of the handle assembly shown inthe previous figure. The handle assembly includes a handle housing, ahandle axle, a proximal cap, and a collet. In the embodiment of FIG. 6,the proximal cap, the collet, and the handle axle cooperate to pinch theshaft between the jaws of the collet. Under normal operating conditions,the handle axle will be fixed to the shaft when the shaft is pinchedbetween the jaws of the collet.

FIG. 7 is an enlarged cross-sectional view showing a portion of theassembly shown in the previous figure. In particular, FIG. 7 provides anenlarged cross-sectional view of the first camming element and thesecond camming element. In the embodiment of FIG. 7, the first cammingelement and the second camming element form part of a torque controlmechanism. In some useful embodiments, the first camming element and thesecond camming element are dimensioned so that the torque controlmechanism will provide a first maximum torque when the shaft is beingrotated in a clockwise direction and a second maximum torque when theshaft is being rotated in a counter-clockwise direction. In someparticularly useful embodiments, the second maximum torque is differentfrom the first maximum torque.

FIG. 8 is an exploded plan view showing several components of anexemplary handle assembly in accordance with the present disclosure.

FIG. 9 includes a table describing the relative freedom of rotationbetween the handle assembly elements shown in the previous figure andthe shaft. This table also describes the relative freedom of rotationbetween various handle assembly elements and the handle housing.

FIG. 10 is a partial cross-sectional view of an exemplary crossingdevice. The crossing device comprises a tip that is fixed to a distalend of a shaft. In the exemplary embodiment of FIG. 10, the shaftincludes a coil comprising a plurality of filars that are wound in agenerally helical shape.

FIG. 11 is an exploded isometric view showing several components of ahandle assembly that is disposed about the shaft shown in the previousfigure.

FIG. 12 is an enlarged isometric view showing the distal cap, the firstcamming element, and the second camming element shown in the previousfigure.

FIG. 13 is an isometric view of the handle axle.

FIG. 14 is a plan view showing a proximal surface of the first cammingelement.

FIG. 15 is an enlarged isometric view showing a second camming element.The second camming element defines a plurality of recesses. Each recessis dimensioned to receive a ramped surface of the first camming elementshown in the previous figure.

FIG. 16 is an enlarged isometric view showing a distal cap. The distalcap defines a plurality of recesses. Each recess is dimensioned toreceive a ramped surface of the second camming element shown in theprevious figure.

DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to the exemplary embodiments of theinvention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts.

The following detailed description should be read with reference to thedrawings in which similar elements in different drawings are numberedthe same. The drawings, which are not necessarily to scale, depictillustrative embodiments and are not intended to limit the scope of theinvention.

FIG. 1 is a schematic representation of a human heart 100. Heart 100includes a plurality of coronary arteries 102, all of which aresusceptible to occlusion. Under certain physiological circumstances andgiven sufficient time, some occlusions may become total or complete,such as total occlusion 101. As used herein, the terms total occlusionand complete occlusion are intended to refer to the same or similardegree of occlusion with some possible variation in the age of theocclusion. Generally, a total occlusion refers to a vascular lumen thatis ninety percent or more functionally occluded in cross-sectional area,rendering it with little to no blood flow therethrough and making itdifficult or impossible to pass a conventional guide wire therethrough.Also generally, the older the total occlusion the more organized theocclusive material will be and the more fibrous and calcified it willbecome. According to one accepted clinical definition, a total occlusionis considered chronic if it is greater than two weeks old from symptomonset.

FIG. 2 is an enlarged view further illustrating a portion of heart 100shown in the previous figure. In FIG. 2, a total occlusion 101 is shownwithin a coronary artery 102. Generally, a proximal segment 104 ofartery 102 (i.e., the portion of artery 102 proximal of total occlusion101) may be easily accessed using endovascular devices and has adequateblood flow to supply the surrounding cardiac muscle. A distal segment106 of artery 102 (i.e., the portion of artery 102 distal of totalocclusion 101) is not easily accessed with interventional devices andhas significantly reduced blood flow as compared to proximal segment104.

FIG. 3 is a cross-sectional view of a blood vessel 120 having a wall122. In FIG. 3, wall 122 of blood vessel 120 is shown having threelayers. The outermost layer of wall 122 is an adventitia 124 and theinnermost layer of wall 122 is an intima 126. The tissues extendingbetween intima 126 and adventitia 124 may be collectively referred to asa media 128. For purposes of illustration, intima 126, media 128 andadventitia 124 are each shown as a single homogenous layer in FIG. 3. Inthe human body, however, the intima and the media each comprise a numberof sub-layers. The transition between the external-most portion of theintima and the internal-most portion of the media is sometimes referredto as the subintimal space. Intima 126 defines a true lumen 130 of bloodvessel 120. In FIG. 3, occlusion 101 is shown blocking true lumen 130.Occlusion 101 divides true lumen 130 into proximal segment 104 anddistal segment 106. In FIG. 3, a distal portion of a crossing device 132is shown extending into proximal segment 104 of true lumen 130.

As shown in FIG. 3, methods described in this document may include thestep of advancing a crossing device to a location proximate an occlusionin a blood vessel. The exemplary methods described in this document mayalso include the step of advancing crossing device 132 between occlusion101 and adventitia 124. In some useful methods, crossing device 132 maybe rotated as the distal end of crossing device 132 is advanced betweenocclusion 101 and adventitia 124. Rotating crossing device 132 assuresthat the coefficient of friction at the interface between the crossingdevice and the surrounding tissue will be a kinetic coefficient offriction rather than a static coefficient of friction.

FIG. 4 is a plan view showing an assembly including crossing device 132shown in the previous figure. In the embodiment of FIG. 4, a handleassembly 134 is coupled to crossing device 132. In FIG. 4, handleassembly 134 is shown disposed about a proximal portion of a shaft 136of crossing device 132. In FIG. 4, a portion of handle assembly 134 ispositioned between the thumb and forefinger of a left hand LH. A secondportion of handle assembly 134 is disposed between the thumb andforefinger of a right hand RH. The fingers of left hand LH and righthand RH are shown wrapping in a clockwise direction loosely around shaft136 in FIG. 4. The thumb of left hand LH is shown pointing in agenerally proximal direction in FIG. 4. The thumb of right hand RH isshown pointing in a generally distal direction in FIG. 4. For thepurposes of this disclosure, clockwise and counter clockwise are viewedfrom the perspective of a viewer positioned near the proximal end ofshaft 136 viewing an imaginary clock located near distal tip 176. Withreference to FIG. 4, it will be appreciated that handle assembly 134 islong enough to receive the thumb and forefingers of a physician's rightand left hands. When this is the case, a physician can use two hands torotate handle assembly 134.

Rotation of crossing device 132 can be achieved by rolling handleassembly 134 between the thumb and forefinger of one hand. Two hands mayalso be used to rotate handle assembly 134 as shown in FIG. 4. In someuseful methods, crossing device 132 can be rotated and axially advancedsimultaneously. Rotating crossing device 132 assures that thecoefficient of friction at the interface between the crossing device andthe surrounding tissue will be a kinetic coefficient of friction and nota static coefficient of friction.

In some useful methods in accordance with the present disclosure,crossing device 132 is rotated at a rotational speed of between about 2revolutions per minute and about 200 revolutions per minute. In someparticularly useful methods in accordance with the present disclosure,crossing device 132 is rotated at a rotational speed of between about 50revolutions per minute and about 150 revolutions per minute. Crossingdevice 132 may be rotated by hand as depicted in FIG. 4. It is alsocontemplated that a mechanical device (e.g., an electric motor) may beused to rotate crossing device 132.

FIG. 5 is an enlarged plan view showing handle assembly 134 shown in theprevious figure. Handle assembly 134 comprises a handle housing 138. Adistal cap 142 is fixed (e.g., with a threaded connection) to the distalend of handle housing 138. A handle axle 140 is partially disposed inhandle housing 138. In the embodiment of FIG. 5, handle axle 140 isselectively fixed to shaft 136 of crossing device 132. A proximal cap144 is fixed (e.g., with a threaded connection) to the proximal end ofhandle axle 140.

FIG. 6 is a partial cross-sectional view of handle assembly 134 shown inthe previous figure. With reference to FIG. 6 it will be appreciatedthat shaft 136 of crossing device 132 extends through handle assembly134. Handle assembly 134 includes handle housing 138, handle axle 140,proximal cap 144, and a collet 146. In the embodiment of FIG. 6,proximal cap 144, collet 146, and handle axle 140 cooperate to pinchshaft 136 between the jaws of collet 146. Under normal operation, handleaxle 140 will be selectively fixed to shaft 136 when shaft 136 ispinched between the jaws of collet 146.

As shown in FIG. 6, collet 146 of handle assembly 134 is disposed in acavity 148 defined by handle axle 140. Handle axle 140 includes femalethreads 152 that are dimensioned to receive male threads 150 of proximalcap 144. In FIG. 6, proximal cap 144 is shown threadingly engaging aproximal portion of handle axle 140. When handle axle 140 and proximalcap 144 comprise right handed threads, a distally directed force F canbe applied to collet 146 by rotating proximal cap 144 in a clockwisedirection. Applying a distally directed force to collet 146 causes thejaws of collet 146 to pinch shaft 136. Collet 146 and handle axle 140both include tapered surfaces that cause collet 146 to pinch shaft 136when collet 146 is urged in a distal direction relative to handle axle140.

Handle assembly 134 of FIG. 6 comprises a torque control mechanism 154.Torque control mechanism 154 includes a first camming element 156 thatis coupled to a distal portion of handle axle 140. In some usefulembodiments, the distal portion of handle axle 140 includes a pluralityof splines 184 (see FIGS. 11 and 13) and first camming element 156includes grooves that are dimensioned to receive the splines of thehandle axle 140. A distal surface 160 of first camming element 156contacts a proximal end 162 of a second camming element 158. In theembodiment of FIG. 6, a spring 168 urges first camming element 156against second camming element 158. Spring 168 also urges second cammingelement 158 against distal cap 142.

FIG. 7 is an enlarged partial cross-sectional view showing a portion ofthe assembly shown in the previous figure. First camming element 156 andsecond camming element 158 are visible in FIG. 7. Second camming element158 defines a plurality of recesses 164A. Each recess 164A isdimensioned to receive a ramped surface 166A of first camming element156. Each recess 164A is partially defined by a wall 122A. Each wall122A includes a ramp engaging surface 170A. In the embodiment of FIG. 7,each ramp engaging surface 170A has a radius.

The distal surface 161 of second camming element 158 contacts a proximalend 163 of distal cap 142. Distal cap 142 defines a plurality ofrecesses 164B. Each recess 164B is dimensioned to receive a rampedsurface 166B of second camming element 158. Each recess 164B ispartially defined by a wall 122B. Each wall 122B includes a rampengaging surface 170B. In the embodiment of FIG. 7, each ramp engagingsurface 170B has a radius.

In the embodiment of FIG. 7, first camming element 156 and secondcamming element 158 form part of a torque control mechanism 154. If apredetermined maximum torque is applied to shaft 136 in a clockwisedirection CW, then the ramp engaging surface 170A of second cammingelement 158 will ride up ramped surfaces 166A of first camming element156. If a predetermined maximum torque is applied to shaft 136 in acounter-clockwise direction CCW, then the ramp engaging surface 170B ofdistal cap 142 will ride up ramped surfaces 166B of second cammingelement 156.

In some useful embodiments, first camming element 156 and second cammingelement 158 are dimensioned so that torque control mechanism 154 willprovide a first maximum torque when shaft 136 is being rotated in aclockwise direction and a second maximum torque when shaft 136 is beingrotated in a counter-clockwise direction. In some useful embodiments,the second maximum torque is different from the first maximum torque.Also in some useful embodiments, the difference between the secondmaximum torque and the first maximum torque corresponds to a differencein strength of shaft 136 when subjected to a counterclockwise torqueversus a clockwise torque.

FIG. 8 is an exploded plan view showing several components of handleassembly 134. Handle assembly 134 comprises handle housing 138 andhandle axle 140. Handle axle 140 may be inserted into handle housing 138so that handle housing 138 is disposed about a portion of handle axle140. Collet 146 may be inserted into cavity 148 defined by handle axle140. Handle axle 140 includes female threads 152 that are dimensioned toreceive male threads 150 of proximal cap 144. Proximal cap 144 may beadvanced into cavity 148 defined by handle axle 140.

A first camming element 156 defines a socket 174 that is dimensioned toreceive the distal portion of handle axle 140. In some usefulembodiments, the distal portion of handle axle 140 includes a pluralityof splines 184 and first camming element 156 includes grooves that aredimensioned to receive splines 184 of the handle axle 140. Handleassembly 134 also includes a second camming element 158 and distal cap142.

FIG. 9 includes a table describing relative freedom of movement betweenvarious elements shown in FIG. 8. The left-most column of this tablelists each of the elements shown in the previous figure. The top row inthis table lists two statements. First, the element is free to rotaterelative to the shaft. Second, the element is free to rotate relative tothe handle housing. The table also includes boolean logic values of Oand 1. A boolean logic value of 1 indicates that the statement is truefor a given element. A boolean logic value of O indicates that thestatement is false for a given element.

As described above, proximal cap 144, collet 146, and handle axle 140cooperate to pinch the shaft between the jaws of collet 146.Accordingly, proximal cap 144, collet 146, and handle axle 140 are notfree to rotate relative to the shaft under normal operating conditions.In the embodiment of FIG. 9, first camming element 156 and handle axle140 engage one another at a splined connection. Accordingly, firstcamming element 156 and handle axle 140 are not free to rotate relativeto one another. In the embodiment of FIG. 9, distal cap 142 and handlehousing 138 engage one another at a threaded connection. Once thisthread is tightened, distal cap 142 is not free to rotate relative tohandle housing under normal operation.

FIG. 10 is a partial cross-sectional view of an exemplary crossingdevice 132. Crossing device 132 of FIG. 10 comprises a tip 176 that isfixed to a distal end of a shaft 136. In the exemplary embodiment ofFIG. 10, shaft 136 comprises a coil 172, a sleeve 178, a tubular body180, and a sheath 182.

Tip 176 is fixed to a distal portion of coil 172. Coil 172 comprises aplurality of filars that are each wound in a generally helical shape. Inthe embodiment of FIG. 10, coil 172 comprises a left-hand wound coil.Embodiments are also possible in which coil 172 comprises a right-handwound coil. In some useful embodiments of crossing device 132, coil 172comprises eight, nine or ten filars wound into the shape illustrated inFIG. 10. Crossing device 132 includes sleeve 178 that is disposed abouta portion of coil 172. Sleeve 178 may comprise, for example, PET shrinktubing, i.e. polyethylene terephthalate.

Sleeve 178 and coil 172 both extend into a lumen defined by a tubularbody 180. Tubular body 180 may comprise, for example hypodermic tubingformed of Nitnol (i.e. nickel titanium alloy). With reference to FIG.10, it will be appreciated that a proximal portion of sleeve 178 isdisposed between tubular body 180 and coil 172. In some embodiments ofcrossing device 132, a distal portion of tubular body 180 defines ahelical cut. This helical cut may be formed, for example, using a lasercutting process. The helical cut may be shaped and dimensioned toprovide an advantageous transition in lateral stiffness proximate thedistal end of tubular body 180.

A proximal portion of coil 172 extends proximally beyond the distal endof tubular body 180. A hub is fixed to a proximal portion of coil 172and a proximal portion of tubular body 180. The hub may comprise, forexample, a luer fitting. A sheath 182 is disposed about a portion oftubular body 180 and a portion of sleeve 178. In some embodiments ofcrossing device 132, sheath 182 comprises HYTREL, a thermoplasticelastomer.

With reference to FIG. 10, it will be appreciated that tubular body 180,coil 172, sleeve 178, and sheath 182 each have a proximal end and adistal end. The proximal end of sheath 182 is disposed between theproximal end of tubular body 180 and the proximal end of sleeve 178.

The distal end of sleeve 178 is positioned proximate tip 176 that isfixed to the distal end of coil 172. The distal end of sheath 182 islocated between the distal end of tubular body 180 and the distal end ofsleeve 178. With reference to FIG. 10, it will be appreciated thatsheath 182 overlays the distal end of tubular body 180.

With reference to FIG. 10, it will be appreciated that tip 176 has agenerally rounded shape. The generally rounded shape of tip 176 mayreduce the likelihood that crossing device 132 will penetrate theadventitia of an artery. Tip 176 may be formed from a suitable metallicmaterial including but not limited to stainless steel, silver solder,and braze. Tip 176 may also be formed from suitable polymeric materialsor adhesives including but not limited to polycarbonate, polyethyleneand epoxy. In some embodiments of crossing device 132, the outer surfaceof tip 176 comprises a generally non-abrasive surface. For example, theouter surface of tip 176 may have a surface roughness of about 25micrometers or less. A tip member having a relatively smooth outersurface may reduce the likelihood that the tip member will abrade theadventitia of an artery.

FIG. 11 is an exploded isometric view showing several components ofhandle assembly 134 that is disposed about shaft 136 shown in theprevious figure. Handle assembly 134 of FIG. 11 comprises torque controlmechanism 154. Torque control mechanism 154 includes first cammingelement 156 and second camming element 158. First camming element 156and second camming element 158 are dimensioned so that torque controlmechanism 154 will provide a first maximum torque when shaft 136 isbeing rotated in a clockwise direction and a second maximum torque whenshaft 136 is being rotated in a counter-clockwise direction. In someuseful embodiments, the second maximum torque is different from thefirst maximum torque. Also in some useful embodiments, the differencebetween the second maximum torque and the first maximum torquecorresponds to a difference in strength of shaft 136 when subjected to acounterclockwise torque versus a clockwise torque.

Handle assembly 134 comprises handle housing 138 and handle axle 140.Handle axle 140 may be inserted into handle housing 138 so that handlehousing 138 is disposed about a portion of handle axle 140. Collet 146may be inserted into a cavity defined by handle axle 140. Handle axle140 includes female threads that are dimensioned to receive male threads150 of proximal cap 144. Proximal cap 144 may be advanced into cavity148 defined by handle axle 140.

First camming element 156 defines socket 174 that is dimensioned toreceive a distal portion of handle axle 140. In some useful embodiments,the distal portion of handle axle 140 includes a plurality of splines184 and first camming element 156 includes grooves that are dimensionedto receive the splines of the handle axle 140. Handle assembly 134 alsoincludes second camming element 158 and distal cap 142.

FIG. 12 is an enlarged isometric view showing distal cap 142, firstcamming element 156, and second camming element 158 shown in theprevious figure. With reference to FIG. 12, it will be appreciated thatsecond camming element 158 comprises a plurality of ramped surfaces 166Band a plurality of faces 190B. Each ramped surface 166B is adjacent to acorresponding face 190B. In the embodiment of FIG. 12, each face 190B isgenerally perpendicular to a distal surface 161 of second cammingelement 158. In the embodiment of FIG. 12, distal cap 142 comprises aplurality of recesses that are dimensioned to receive ramped surfaces166B. With reference to FIG. 12, it will be appreciated that firstcamming element 156 comprises a plurality of ramped surfaces 166A and aplurality of faces 190A. Each ramped surface 166A is adjacent to acorresponding face 190A. In the embodiment of FIG. 12, each face 190A isgenerally perpendicular to a distal surface 160 of first camming element156. Second camming element 158 comprises a plurality of recesses thatare dimensioned to receive ramped surfaces 166A in the embodiment ofFIG. 12.

FIG. 13 is an isometric view of handle axle 140. With reference to FIG.13, it will be appreciated that a distal portion of handle axle 140includes the plurality of splines 184.

FIG. 14 is a plan view showing a proximal surface of first cammingelement 156. With reference to FIG. 14, it will be appreciated thatfirst camming element 156 defines socket 174. In the embodiment of FIG.14, socket 174 is dimensioned to received the distal portion of handleaxle 140. With reference to FIG. 14, it will be appreciated that socket174 includes grooves 186 that are dimensioned to receive the splines ofhandle axle 140 shown in the previous figure.

FIG. 15 is an enlarged isometric view showing second camming element158. Second camming element 158 defines a plurality of recesses 164A.Each recess 164A is dimensioned to receive a ramped surface of firstcamming element 156 shown in the previous figure. Each recess 164A ispartially defined by wall 122A. Each wall 122A includes a ramp engagingsurface 170A. In the embodiment of FIG. 15, each ramp engaging surface170A has a radius.

FIG. 16 is an enlarged isometric view showing distal cap 142. Distal cap142 defines a plurality of recesses 164B. Each recess 164B isdimensioned to receive a ramped surface 166B of second camming element158 shown in the previous figure. Each recess 164B is partially definedby a wall 122B. Each wall 122B includes a ramp engaging surface 170B. Inthe embodiment of FIG. 16, each ramp engaging surface 170B has a radius.

The operation of handle assembly 134 will now be described. A physicianmay fix handle assembly 134 about the proximal portion of shaft 136 ofcrossing device 132. Alternatively, crossing device 132 may be deliveredto the physician with handle assembly 134 positioned on shaft 136.

During a therapy procedure, the physician may periodically adjust theposition of handle assembly 134 along the length of shaft 136. To movethe position of handle assembly 134 along shaft 136, the physician mayloosen proximal cap 144 from handle axle 140 such that the taperedsurfaces of the jaws of collet 146 are not in contact with the taperedsurface of cavity 148 of handle axle 140. The physician may slide handleassembly 134 in a lengthwise direction along shaft 136 to a desiredlocation. The physician may then tighten proximal cap 144 within handleaxle 140. In this manner, the tapered surfaces of the jaws of collet 146may contact the tapered surface of cavity 148 and cause the jaws ofcollet 146 to pinch shaft 136 and fix the position of shaft 136 relativeto handle assembly 134.

During a therapy procedure, the physician may position the distalportion of shaft 136 of crossing device 132 within artery 102. Handleassembly 134 may be used to advance the distal portion of crossingdevice 132 to a location proximal of occlusion 101. Alternatively, oradditionally, handle assembly 134 may be used to advance the distalportion of crossing device 132 between occlusion 101 and adventitia 124to a location distal occlusion 101. In this manner, a physician may griphandle assembly 134 via handle housing 138 with the thumb and forefingerof one hand, or alternatively, with two hands. As shaft 136 is advancedinto the vasculature of the patient, the physician may periodicallyadjust the position of handle assembly 134 along the length of shaft 136as described above.

At various times during a therapy procedure, the physician may rotatehandle housing 138 to rotate crossing device 132, including shaft 136and tip 176. Rotating crossing device 132 assures that the coefficientof friction at the interface between the crossing device and thesurrounding tissue will be a kinetic coefficient of friction and not astatic coefficient of friction. In this manner, crossing device 132 maymore easily pass through artery 102, occlusion 101, and/or variouslayers of the wall of artery 102. The physician may rotate handlehousing 138 in a clockwise (CW) or in a counter-clockwise (CCW)direction.

For purposes of this disclosure, the clockwise and counter-clockwise areoriented from the perspective of a physician having the left hand (LH)and right hand (RH) shown in FIG. 4. This physician holding handleassembly 134 in his left hand (LH) and right hand (RH) is contemplatingthe rotation of the tip 176. In FIG. 4, the fingers of each hand areshown wrapping in a clockwise direction around shaft 136. In otherwords, clockwise and counter clockwise are viewed from the perspectiveof a viewer positioned near the proximal end of the device viewing animaginary clock near the distal end of the device.

The physician causes shaft 136 and tip 176 to rotate by rotating handlehousing 138. During this rotation, shaft 136 and tip 176 may experienceresistance to rotation. This resistance may, for example, be caused byfrictional contact between crossing device 132 and features of thepatient's anatomy (e.g., the walls of a blood vessel and occlusionslocated inside the blood vessel). When resistance is encountered, thephysician may apply greater torque to shaft 136, up to a predeterminedmaximum torque. In the exemplary embodiment of FIGS. 3 through 14, thispredetermined maximum torque is controlled by a torque control mechanism154.

The operation of torque control mechanism 154 may be described withreference to the exemplary embodiment shown in FIGS. 3 through 14. Inthis exemplary embodiment, distal cap 142 is fixed to handle housing 138by a threaded connection. Accordingly, rotation of handle housing 138 ina CCW direction causes distal cap 142 to also rotate in a CCW direction.Wall 122B of distal cap 142 may then contact face 190B of ramp 166B,causing second camming element 158 to rotate in a CCW direction. Therotation of second camming element 158 may rotate ramp engaging surface170A of second camming element 158 into contact with ramp 166A of firstcamming element 156. Specifically, ramp engaging surface 170A maycontact, or “ride,” a lower portion of the length of ramp 166A. Thecontact between ramp engaging surface 170A and ramp 166A causes firstcamming element 156 to rotate in the CCW direction. Because handle axle140 is fixed to first camming element 156 by the plurality of splines184, rotation of first camming element 156 causes handle axle 140 torotate in the CCW direction. As described above, shaft 136 is fixed tohandle axle 140 by collet 146. Accordingly, rotation of handle axle 140in the CCW direction causes shaft 136 to rotate in the CCW direction.

As handle housing 138 continues to rotate in the CCW direction, theresistance to rotation that shaft 136 and tip 176 experience mayincrease. As this resistance increases, the torque required to rotateshaft 136 may increase. As the torque applied to handle housing 138increases, ramp engaging surface 170A may ride further up the length oframp 166A (i.e. from a lower portion to a higher portion). When this isthe case, ramp engaging surface 170A of second camming element 158 andramp 166A of first camming element 156 will cooperate to compress spring168.

In the exemplary embodiment shown in FIGS. 3 through 14, torque controlmechanism 154 limits the magnitude of torques that may be applied toshaft 136 by rotating handle housing 138. Torque control mechanism 154limits the torque in a first direction to a magnitude equal to or lessthan a first maximum torque and limits the torque in a second directionto a magnitude equal to or less than a second maximum torque. In someuseful embodiments, the second maximum torque is different from thefirst maximum torque. In these embodiments, the shape (e.g., the height)of each ramp 166B of second camming element 158 may be different fromthe shape of each ramp 166A of first camming element 156.

When the first maximum torque is applied to shaft 136, sufficient forceis exerted against spring 168 to allow ramp engaging surface 170A toride up the entire length of ramp 166A and over the highest point oframp 166A. When ramp engaging surface 170A rides over the highest pointof ramp 166A, spring 168 causes proximal end 162 of second cammingelement 158 to rapidly contact distal end 160 of first camming element156. This rapid contact may generate an audible “clicking” sound. Thisrapid contact may also cause a tactile response (e.g., vibrations inhousing handle 138) that can be felt in the finger tips of left hand(LH) and right hand (RH). This audible and/or tactile response may serveto notify the physician that the first maximum torque has been exceeded.

When the first maximum torque has been reached, continued rotation ofhandle housing 138 in the CCW direction will cause no furthersubstantial rotation of shaft 136. Instead, continued rotation of handlehousing 138 will only produce more “clicking” by torque controlmechanism 154. Between a minimum amount of torque necessary to rotateshaft 136 and the first maximum torque may represent a range of torquethat may be applied to shaft 136 to cause rotation of shaft 136 in theCCW direction.

When the first maximum torque has been reached, the physician may chooseto discontinue rotating handle housing 138 in the CCW direction. At thispoint, the physician may choose to begin rotating handle housing 138 inthe CW direction. In some applications, reversing the direction ofrotation is a useful strategy for crossing restrictions.

As mentioned above, torque control mechanism 154 also limits themagnitude of torque that may be applied to shaft 136 when handle housing138 is rotated in a clockwise (CW) direction. The operation of torquecontrol mechanism 154 when handle housing 138 is rotated in the CWdirection may be described with continuing reference to the exemplaryembodiment shown in FIGS. 3 through 14. In this exemplary embodiment,distal cap 142 is fixed to handle housing 138 by a threaded connection.Accordingly, rotation of handle housing 138 in the CW direction causesdistal cap 142 to also rotate in the CW direction. Rotation of distalcap 142 in the CW direction will rotate ramp engaging surface 170B ofdistal cap 142 into contact with ramp 166B of second camming element158. Specifically, the radius of ramp engaging surface 170B may contact,or “ride,” a lower portion of the length of ramp 166B. This contactcauses second camming element 158 to rotate in the CW direction.Rotating second camming element 158 in the CW direction causes a wall122A of second camming element 156 to contact a face 190A of firstcamming element 156, causing first camming element 156 to rotate in theCW direction. Because handle axle 140 is fixed to first camming element156 by the plurality of splines 184, rotation of first camming element156 causes handle axle 140 to rotate. As describe above, shaft 136 isfixed to handle axle 140 by collet 146. Therefore, shaft 136 rotates inthe CW direction when handle axle 140 is rotated in the CW direction.

As handle housing 138 continues to rotate in the CW direction, theresistance to rotation that shaft 136 experiences may increase. As thisresistance increases, the torque required to overcome the resistance mayincrease and may result in a higher torque being applied to shaft 136.As the torque increases, ramp engaging surface 170B will ride further upthe length of ramp 166B (i.e. from a lower portion to a higher portion).When this is the case, ramp engaging surface 170B and ramp 166B ofsecond camming element 158 will cooperate to compress spring 168.

When the second maximum torque is applied to shaft 136, sufficient forceis exerted against spring 168 to allow ramp engaging surface 170B toride up the entire length of ramp 166B and over the highest point oframp 166B. At this point, continued rotation of handle housing 138 inthe CW direction will result in substantially no further rotation ofshaft 136. Instead, continued rotation of handle housing 138 will onlyproduce more “clicking” by torque control mechanism 154.

The “clicking” by torque control mechanism 154 is produced, for example,as second camming element 158 rapidly contacts distal cap 142. When rampengaging surface 170B rides over the highest point of ramp 166B, spring168 causes distal end 161 of second camming element 158 to rapidlycontact proximal end 163 of distal cap 142. In some exemplaryembodiments, this rapid contact generates an audible “clicking” sound.This rapid contact may also cause a tactile response (e.g., vibrationsin housing handle 138) that can be felt in the finger tips of left hand(LH) and right hand (RH). This audible and/or tactile response may serveto notify the physician that the second maximum torque has beenexceeded. Between a minimum amount of torque necessary to rotate shaft136 and the second maximum torque may represent a range of torque thatmay be applied to shaft 136 to cause rotation of shaft 136 in the CWdirection.

The first maximum torque and the second maximum torque may be varied byvarying a number of attributes of torque control mechanism 154. Examplesof attributes include the spring constant of spring 168, a magnitude ofpre-loading placed on spring 168, the maximum height of each ramp (166A,166B), and the slope/pitch/angle of each ramp (166A, 166B). The firstand second maximum torques may be simultaneously increased or decreasedby replacing spring 168 with a spring producing greater or lesser springforce. The first and second maximum torques may be independently changedby altering the dimensions of one or more of the components of torquecontrol mechanism 154, such as, for example, the maximum height of eachramp (166A, 166B), the slope/pitch/angle of each ramp (166A, 166B),characteristics of ramp engaging surface 170A and/or ramp engagingsurface 170B, or any other modification that would result in a greateror lesser first and/or second maximum torques.

The desired first maximum torque and the desired second maximum torquemay be related to the strength of shaft 136 relative to the rotationaldirection. By way of example, when shaft 136 is rotated in a CCWdirection, coil 172 of shaft 136 may expand and may be weaker. In thiscase, the first maximum torque, i.e. the maximum torque applied in theCCW direction should be low enough to not break the expanded coil 172.In a further example, when shaft 136 is rotated in a CW direction, coil172 of shaft 136 may compress and may be stronger relative to the steadyor expanded state of coil 172. In this case, the second maximum torque,i.e. the maximum torque applied in the CW direction should be low enoughto not break the compressed coil 172. In this example, the secondmaximum torque would be higher than the first maximum torque. It isfurther contemplated that the first and second maximum torques may notbe the exact torque necessary to cause coil 172 to fail in a respectivedirection, but that there may be safety factor included in determiningthe torques.

From the foregoing, it will be apparent to those skilled in the art thatthe present invention provides, in exemplary non-limiting embodiments,devices and methods for the treatment of chronic total occlusions.Further, those skilled in the art will recognize that the presentinvention may be manifested in a variety of forms other than thespecific embodiments described and contemplated herein. Accordingly,departures in form and detail may be made without departing from thescope and spirit of the present invention as described in the appendedclaims.

Other embodiments of the invention will be apparent to those skilled inthe art from consideration of the specification and practice of theinvention disclosed herein. It is intended that the specification andexamples be considered as exemplary only, with a true scope and spiritof the invention being indicated by the following claims.

What is claimed:
 1. A device for facilitating treatment of a bloodvessel, the device comprising: a shaft having a distal end and aproximal end; and a handle assembly disposed about the shaft; whereinthe handle assembly includes a first portion and a torque limitingmechanism coupling the first portion to the shaft; wherein the torquelimiting mechanism includes a first ramp that allows relative movementbetween the first portion and the shaft when the first portion is beingrotated in a first direction and a torque applied to the shaft isgreater than a first maximum torque; and wherein the torque limitingmechanism allows relative movement between the first portion and theshaft when the first portion is being rotated in a second direction anda torque applied to the shaft is greater than a second maximum torque.2. The device of claim 1, wherein the second maximum torque is differentthan the first maximum torque.
 3. The device of claim 1, wherein: theshaft includes a left hand wound coil; the first direction is aclockwise direction; and the first maximum torque is greater than thesecond maximum torque.
 4. The device of claim 1, wherein: the shaftincludes a right hand wound coil; the second direction is acounterclockwise direction; and the second maximum torque is greaterthan the first maximum torque.
 5. The device of claim 1, wherein: theshaft comprises a coil and the device further comprises a distal tipfixed to a distal end of the coil and a proximal hub fixed to a proximalend of the coil.
 6. The device of claim 1, wherein the torque limitingmechanism comprises a first camming element, the first camming elementhaving a first ramp, the first ramp having a first ramped surface and afirst face.
 7. The device of claim 6, wherein the first camming elementis coupled to the shaft so that the first camming element is not free torotate relative to the shaft.
 8. The device of claim 6, wherein thetorque limiting mechanism comprises a second camming element having afirst ramp engaging surface and a second ramp, the second ramp having asecond ramped surface and a second face.
 9. The device of claim 8,wherein the torque limiting mechanism comprises a cap fixed to the firstportion, the cap comprising a second ramp engaging surface.
 10. Thedevice of claim 9, wherein: the first ramp engaging surface engages thefirst ramped surface when the first portion is rotated in the firstdirection; and the second ramp engaging surface engages the secondramped surface when the first portion is rotated in a second direction.11. The device of claim 10, wherein: the first face contacts a firststop when the first portion is rotated in the second direction; and thesecond face contacts a second stop when the first portion is rotated inthe first direction.
 12. The device of claim 8, wherein: the firstramped surface has a first pitch; the second ramped surface has a secondpitch; and the second pitch is different from the first pitch.
 13. Thedevice of claim 8, wherein: the first ramp has a first maximum height;the second ramp has a second maximum height; and the second maximumheight is different than the first maximum height.
 14. A device forfacilitating treatment of a blood vessel, the device comprising: a shafthaving a distal end and a proximal end; a handle assembly disposed aboutthe shaft; and the handle assembly comprising a handle housing and atorque limiting mechanism coupling the handle housing to the shaft;wherein the torque limiting mechanism allows relative movement betweenthe handle housing and the shaft when the handle housing is beingrotated in a first direction and a torque applied to the shaft hasexceeded a first maximum torque; wherein the torque limiting mechanismcomprises a first camming element, wherein the first camming element isfree to rotate relative to the handle housing; wherein the torquelimiting mechanism comprises a second camming element, wherein thesecond camming element is free to rotate relative to the handle housing;wherein the torque limiting mechanism comprises a distal cap, whereinthe distal cap is not free to rotate relative to the handle housing. 15.The device of claim 14, wherein the torque limiting mechanism allowsrelative movement between the handle housing and the shaft when thehandle housing is being rotated in a second direction and the torqueapplied to the shaft has exceeded a second maximum torque, wherein thesecond maximum torque is different than the first maximum torque. 16.The device of claim 14, wherein, the first camming element has a firstramp, the first ramp having a first ramped surface and a first face. 17.The device of claim 16, wherein the first camming element is coupled tothe shaft so that the first camming element is not free to rotaterelative to the shaft.
 18. The device of claim 16, wherein the secondcamming element has a first ramp engaging surface and a second ramp, thesecond ramp having a second ramped surface and a second face.
 19. Thedevice of claim 18, wherein the cap comprises a second ramp engagingsurface.
 20. The device of claim 19, wherein: the first ramp engagingsurface engages the first ramped surface when the handle housing isrotated in the first direction; and the second ramp engaging surfaceengages the second ramped surface when the handle housing is rotated ina second direction.